US20130133864A1

US20130133864A1 - Heat distribution structure, manufacturing method for the same and heat-dissipation module incorporating the same

Info

Publication number: US20130133864A1
Application number: US13/402,603
Authority: US
Inventors: Kai-Shing Yang; Kuo-Hsiang Chien
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2011-11-25
Filing date: 2012-02-22
Publication date: 2013-05-30
Also published as: TWI429848B; CN103137846A; TW201321663A

Abstract

A heat distribution structure, a method for manufacturing the same and a heat-dissipation module incorporating the same are disclosed. The heat distribution structure includes a first cap with a first grove and a second cap with a second groove and a support body interposed between the first cap and the second cap, wherein microstructures are formed at the bottoms of the first groove and the second groove and through holes are formed in the support body. The support body is interposed between the first and second caps, such that a cavity is formed by the first cap, the support body and the second cap. A working fluid is contained in the cavity that flows therein through capillary action provided by the microstructures of the first and second grooves and the through holes in the support body, thus evenly distributing heat in the heat distribution structure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to heat distribution structures, manufacturing methods for the same and heat-dissipation modules incorporating the same, and, more particularly, to a heat distribution structure that enhances the effect of heat distribution, a manufacturing method for the same and heat-dissipation module incorporating the same.
2. Description of Related Art
Light emitting diodes (LED) typically have the advantages of low power consumption, fast response speed, and small volume and have become a main alternative to conventional incandescent or fluorescent bulbs. However, the LEDs convert about half of its input power into heat during light emission. Although such heat is in the level of only a few watts, due to small volumes of the LEDs, heat density is relatively high and leading to hot spots with extremely high temperature at die attachment area. This reduces the efficiency of the LEDs and/or shortens the service life of the LEDs.
To prevent overheating of the LED dies, an LED is disposed on a heat dissipating substrate in the prior art, such as a copper foil printed circuit board, a metal-based printed circuit board or a ceramic substrate. However, the heat transfer coefficient of a copper foil printed circuit board is approximately 0.36 W/mk. This indicates poor heat transfer and causes overheating of the LED. FIG. 1 is a schematic diagram illustrating the use of a metal-based printed circuit board. In a heat-dissipating module 1, an LED 11 is fixed to a substrate 13 via an adhesive 12, and the substrate 13 is disposed on a heat-dissipating substrate including a dielectric layer 14 and a metal layer 15, and the heat-dissipating substrate is then attached to a heat-dissipating structure 17 via a thermal interface material (TIM) 16.
In FIG. 1, heat (as indicated by arrows) generated by the LED 11 is propagated sequentially through the substrate 13, the dielectric layer 14 and the metal layer 15 to the heat-dissipating structure 17. In this propagation path, heat is met with at least three layers of dissipating resistances. In addition, the dielectric layer 14 has difficulty of evenly distributing spot heat source generated at the attachment location of the LED 11 to the plane of the metal layer 15. Moreover, the dielectric layer is usually made of epoxy resin with poor thermal conductivity, so that it often becomes a heat-dissipating bottleneck for the heat-dissipating module, and renders the overall heat transfer coefficient to be only 1 to 12 W/mk. In addition, relevant art also proposes using a ceramic substrate as the heat-dissipating substrate. Although it has relatively better dielectric characteristics and lower thermal expansion coefficient, and a good heat transfer performance (with a heat transfer coefficient of about 170 W/mk), but ceramic substrates did not address the “hot spot” issue faced by current high-power LEDs. Alternatively, even if materials of high thermal conductivities such as diamond like carbon films are used, which have heat transfer coefficients as high as between 200 to 600 W/mk in the horizontal direction, and heat transfer coefficients lower than 10 W/mk in the vertical direction, they are still not sufficient in overcoming the “hot spot” problem faced by the current high-power LEDs.
U.S. Pat. Nos. 6,274,924, 6,943,433, 7,361,490 and 7,208,772 and U.S. Patent Publication Nos. 2006/0086945 and 2005/0269587 mainly focus on the design of incorporating heat-dissipating blocks in package structures, but their heat transfer characteristics are all limited by the heat transfer characteristics of the metal materials used for the heat-dissipating blocks. Furthermore, U.S. Pat. Nos. 6,717,246 and 6,789,610 as well as U.S. Patent Publication No. 2006/0243425 disclose the use of a flat plate heat pipe, which allows heat transfer through the phase change of a working fluid inside the pipe. Using two-phase change and flowing of the working fluid for heat transfer, heat spread is better than metal plate of the same size, and temperature distribution is more even. However, existing flat plate heat pipe is usually made of copper, which can be challenging in terms of integration in the die manufacturing process.

SUMMARY OF THE INVENTION

The present invention provides a heat distribution structure, which comprises a first cap formed with a first groove, a second cap formed with a second groove, a plurality of microstructures formed at bottoms of the first groove and the second groove, a support body formed with a plurality of through holes interposed between the first cap and the second cap, wherein the first groove and the second groove face the support body, such that a cavity is formed by the first cap, the support body and the second cap, and a working fluid accommodated in the cavity that flows within the cavity via the plurality of microstructures and the plurality of through holes.
A heat-dissipation module for dissipating heat generated by a die according to an embodiment of this disclosure can be formed by combining the heat distribution structure of this disclosure and a heat-dissipation structure by a thermal interface material. The heat-dissipation module includes: a heat-dissipation structure; the thermal interface material applied onto the heat-dissipation structure; the heat distribution structure proposed by this disclosure provided on the heat-dissipation structure with the thermal interface material interposed therebetween, wherein an insulating layer is provided on a surface of the heat distribution structure away from the thermal interface material; a metal layer formed on the insulating layer of the heat distribution structure; and the die provided on the metal layer.
A method for manufacturing a heat distribution structure according to an embodiment of this disclosure includes the following steps: (1) forming a plurality of microstructures at bottoms of a first groove of a first cap and a second groove of a second cap, forming a guiding hole on the first cap or the second cap, and forming a plurality of through holes in a support body; (2) interposing the support body between the first cap and the second cap in a manner of the first groove and the second groove facing the support body so as to form a cavity between the first cap, the support body and the second cap; and (3) introducing a working fluid into the cavity via the guiding hole, and then sealing the guiding hole, such that the working fluid flows within the cavity via the microstructures and the through holes.
Compared with the prior art, the heat distribution structure of this disclosure and the manufacturing method for the same allow heat to be evenly distributed by allowing the working fluid to flow within the cavity of the heat distribution structure through capillary action caused by the plurality of microstructures and through holes, solving the “hot spot” problem. Moreover, the heat-dissipation module incorporating the heat distribution structure of this disclosure eliminates the multiple dissipating resistances in the traditional heat-dissipation modules, improving efficiency of heat dissipation of the heat-dissipation module, which in turn stabilizes the performance of the LEDs.

BRIEF DESCRIPTION OF THE DRAWINGS

This disclosure can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating a conventional heat-dissipation module;

FIG. 2 is a schematic diagram illustrating a heat distribution structure of this disclosure;

FIG. 3 is a flowchart illustrating a method for manufacturing a heat distribution structure of this disclosure;

FIG. 4 is a schematic diagram illustrating a heat-dissipation module incorporating a heat distribution structure of this disclosure; and

FIGS. 5A and 5B are graphs depicting test results of the temperatures of a conventional heat-dissipation module and the heat-dissipation module according to this disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

This disclosure is described by the following specific embodiments. Those with ordinary skills in the arts can readily understand the other advantages and functions of this disclosure after reading the disclosure of this specification. This disclosure can also be applied or implemented in different embodiments.
In light of the drawbacks in the art, embodiments according to this disclosure provide a heat distribution structure, a manufacturing method for the same and a heat-dissipation module incorporating the same that achieve good and even heat distribution, which increases the performance of a die provided in the heat-dissipation module. It should be noted that the structures, proportions, sizes and the like shown in the drawings of this disclosure are only to accompany the contents disclosed in this specification and to facilitate understanding and reading by those with ordinary skill in the art. They are not to limit the conditions in which this disclosure can be embodied, so they have no technical substantial meanings. Any modifications to the structures, proportions, sizes and the like are construed as falling within the scope of this disclosure so long as they do not affect the effects generated and the objectives achieved by this disclosure. Similarly, terms such as “above”, “below”, “first” and “second” cited in this specification are to facilitate understanding of the descriptions and are not used to limit the scope of this disclosure. Any modifications or changes in relative relationships are construed to be within the scope of this disclosure so long as there is no substantial technical change.
A heat distribution structure, a manufacturing method for the same and a heat-dissipation module incorporating the same according to embodiments of this disclosure are described in details below with reference to the drawings.
Referring to FIG. 2, a cross-sectional diagram illustrating a heat distribution structure of this disclosure is shown. The heat structure 20 includes a first cap 21, a support body 22, a second cap 23 and a working fluid 25.
The first cap 21 includes a first groove 210, wherein a plurality of microstructures 211 a are formed at the bottom 211 of the first groove 210. The second cap 23 has a second groove 230, wherein a plurality of microstructures 231 a are formed at the bottom 231 of the second groove 230. The microstructures 211 a and 231 a can be formed at the bottom 211 of the first groove 210 and the bottom 231 of the second groove 230, respectively by etching or other techniques. As shown in FIG. 2, microstructures 211 a and 231 a can be protrusions protruded from the bottoms 211 and 231, respectively. It should be noted that the first cap 21 and the second cap 23 are the same components in principle, and the directions in which the plurality of microstructures 211 a and 231 a extend are substantially parallel to each other, but are not limited to being aligned to the same normal. In addition, the first cap 21 and the second cap 23 are made of silicon and fabricated by lithography processes.
The support body 22 includes a plurality of through holes 220. The through holes 220 can be formed in the support body 22 by laser or other techniques, wherein the directions in which the plurality of through holes 220 extend are substantially parallel to each other. The support body 22 is interposed between the first cap 21 and the second cap 23, and the first groove 210 of the first cap 21 and the second groove 230 of the second cap 23 face each other with the support body 22 interposed therebetween. The first cap 21, the second cap 23 and the support body 22 can be formed into an integrated structure using a high-temperature and high pressure anode manufacturing process. In addition, as shown in FIG. 2, the first cap 21 and the second cap 23 sandwich the support body 22 between the first cap 21 and the second cap 23, allowing a cavity 24 to be formed between the first cap 21, the support body 22 and the second cap 23. The cavity 24 approaches around 10⁻³Ton of vacuum state. Moreover, the material of the support body 22 is glass or glass with 4% of Na₂O.
The working fluid 25 is contained within the cavity 24. The working fluid 25 flows in the cavity 24 through the plurality of microstructures 211 a and 231 a and the plurality of through holes 220. The working fluid 25 is for example water. More specifically, a guiding hole (not shown) can be formed in the first cap 21 or the second cap 23 to introduce the working fluid 25 into the cavity 24. After the working fluid 25 is introduced into the cavity 24, the guiding hole is then sealed.
It should be noted that the directions in which the plurality of microstructures 211 a and 231 a in the cavity 24 and the through holes 220 extend are substantially parallel to each other, the working fluid exhibit capillary phenomenon in the cavity 24 by the microstructures 211 a and 231 a and the through holes 220, so the working fluid 25 can flow within the cavity 24 due to capillary action caused by the microstructures 211 a and 231 a and the through holes 220. It should be noted that there are no particular limit to the sizes of the microstructures 211 a and 231 a and the through holes 220 and the volume of the working fluid 25 guided into the cavity 24. As shown in FIG. 2, the volume of the working fluid 25 does not completely cover the plurality of microstructures 231 a. Moreover, the working fluid 25 may flow within the cavity 24. Thus, when the heat structure 20 is flipped over, the working fluid 25 will then cover the plurality of microstructures 211 a due to gravity.
In an embodiment, if the spot heat source generated by a die is underneath the second cap 23 of FIG. 2, then heat may be distributed in the following process: the working fluid 25 spreads the spot heat source out into a plane via capillary action at the plurality of the microstructures 231 a, then the plurality of through holes 220 absorb the working fluid 25 through capillary action to the plurality of the microstructures 211 a, and then the plurality of microstructures 211 a distribute the working fluid 25 into the first groove 210, and thereafter the working fluid 25 descends back to the second groove 230, to thereby complete a circulation. During a circulation of the working fluid 25 in the cavity 24, the working fluid 25 may change from the liquid phase to the gaseous phase when heated, and after flowing to the unheated side, it changes from the gaseous phase back to the liquid phase, thus achieving the effect of heat dissipation.
Moreover, the sidewalls 241 of the cavity 24 (including the sidewall of the first groove 210, the sidewall of the second groove 230 or the sidewalls of the first groove 210 and the second groove 230) may be also formed with a plurality of microstructures 212 and 232 for increasing the capillary action in the cavity 24 and thus enhancing the flow of the working fluid 25 in the cavity 24.
From FIG. 2 it can be understood that in the heat distribution structure of this disclosure, through the microstructures and the through holes in the cavity, the working fluid in the cavity exhibit capillary action so that heat in the heat distribution structure can be evenly distributed, eliminating the “hot spot” problem produced when a die is provided, and thus improving die performance. In addition, the heat distribution structure made of silicon and glass facilitates the installation of the die.
Referring to FIG. 3, a flowchart illustrating the method for manufacturing the heat distribution structure of this disclosure is shown. First, a support body, a first cap and a second cap are provided. The material of the first cap and the second cap can be silicon, for example. The material of the support body can be glass or glass with 4% of Na₂O.
In step S31, a first groove is formed in the first cap and a second groove is formed in the second cap; a plurality of microstructures are formed at the bottoms of the first and second grooves; a guiding hole is formed in the first cap or the second cap; and a plurality of through holes are formed in the support body. Next, proceed to step S32.
In detail, by a technique of etching, the first groove and the second groove are formed in the first cap and the second cap, respectively, and the microstructures are formed at the bottoms of the first and second grooves. In addition, a guiding hole can be formed at an arbitrary location of the first cap or the second cap for letting in a working fluid. Furthermore, the through holes are formed in the support body by laser. It should be noted that the order in which the sub-step for forming the plurality of microstructures at the bottom of the first groove, the sub-step for forming the plurality of microstructures at the bottom of the second groove and the sub-step for forming the plurality of through holes inside the support body are carried out has no particularly limit.
In step S32, the support body is sandwiched between the first cap and the second cap in such a way that the first groove and the second groove face the support body, thereby forming a cavity between the first cap, the support body and the second cap. Next, proceed to step S33.
More particularly, the material of the first and the second caps are typically silicon. The material of the support body is typically glass or glass with 4% of Na₂O. The glass and the silicon can be combined together with high heat (e.g. around 300 to 500° C.) and high pressure (e.g. around 500 to 1000V). The 02 in the glass and the Si₄ ⁺ in the silicon form SiO₂and covalently bond together. The combined silicon and glass has a strength of about 20 to 50 MPa. The first cap and the support body, and the second cap and the support body can be combined together in this manner. Moreover, the first cap and the second cap using silicon as the main material can be easily integrated into the die manufacturing process. In addition, in the cavity formed after combining the first cap, the support body and the second cap, the directions in which the plurality of microstructures at the bottom of the first groove, the plurality of microstructures at the bottom of the second groove and the plurality of through holes in the support body extend are substantially parallel to each other.
In step S33, a fluid (e.g. water) is guided into the cavity via the guiding hole, and then the guiding hole is sealed, so that the fluid flows within the cavity owing to the plurality of microstructures and the plurality of through holes. Before the guiding hole is sealed, the cavity is made to be in a vacuum state of around 10⁻³Ton.
It is known from FIG. 3, through the method for manufacturing the heat distribution structure of this disclosure, an enclosed cavity can be formed in the heat distribution structure, and the bottoms the first groove and the second groove constitute the cavity have the plurality of microstructures, while the support body between the first groove and the second groove has the plurality of through holes, such that the working fluid in the cavity can flow within the first groove, the second groove and the through holes, thereby achieving even distribution of heat.
Referring to FIG. 4, a cross-sectional diagram illustrating a heat-dissipation module incorporating the heat distribution structure of this disclosure is shown. FIG. 4 shows the heat structure 20 of FIG. 3 or the heat distribution structure manufactured according to the steps shown in FIG. 3 is applied to a heat-dissipation module 3 carrying a die.
The heat-dissipation module 3 includes a die 31, a metal layer 32, an insulating layer 33, a heat distribution structure 30, a thermal interface material 34 and a heat-dissipation structure 35.
The heat-dissipation structure 35 can be a heat sink. The thermal interface material (TIM) 34 is applied onto the heat-dissipation structure 35, and the heat distribution structure 30 is disposed on the heat-dissipation structure 35 with the thermal interface material 34 interposed therebetween. The thermal interface material 34 fills the bonding gap between the heat distribution structure 30 and the heat-dissipation structure 35, thus expanding the heat-dissipation area between the heat distribution structure 30 and the heat-dissipation structure 35.
The heat distribution structure 30 has all the characteristics of the heat structure 20 shown in FIG. 2. Sidewalls 301 of a cavity 300 of the heat distribution structure 30 also have a plurality of microstructures 301 a. In addition, an insulating layer 33 is provided on a face 302 of the heat distribution structure 30 away from the thermal interface material 34. The insulating layer 33 is a layer of silicon dioxide.
The metal layer 32 is formed on the insulating layer 33 of the heat distribution structure 30. More particularly, metal (e.g. copper) can be formed by sputtering, electroplating or other techniques on the insulating layer 33 of the heat distribution structure 30 as a circuit layer. The die 31 is provided on the metal layer 32. In the case of an LED used as the die, it can be attached to the metal layer 32 by eutectic alloys.
Therefore, in FIG. 4, the spot heat source generated by the die 31 can be distributed into a plane heat source by the heat distribution structure 30, and then the heat can be transferred through large area contact with the thermal interface material 34 and the heat-dissipation structure 35, and finally dissipated through the heat-dissipation structure 35.
Now, as shown in FIGS. 5A and 5B, graphs depicting test results of the temperatures of a conventional heat-dissipation module and the heat-dissipation module according to this disclosure are shown, in which the heat-dissipation module carrying an LED is compared with a traditional heat-dissipation module carrying an LED as shown in FIG. 1 in the prior art.
Referring to FIGS. 5A and 5B, in the prior art heat from the die to the heat-dissipation structure must encounter at least three spreading resistances (i.e. the substrate, the dielectric layer and the metal layer), whereas the heat-dissipation module of this disclosure encounters only the insulating layer and the heat-dissipation structure, thus greatly reducing dissipating resistance and increasing heat transfer efficiency. Moreover, epoxy resin is typically used as the dielectric layer in the prior art, which has poor heat conductivity such that hot spots generated by the die cannot be distributed evenly, this results in the temperature difference between the heat-dissipation structure and the die of FIG. 5A being much greater than the temperature difference between the heat-dissipation structure and the die of FIG. 5B, implying heat of the prior art still concentrates around the die itself and the die attachment area. This generates hot spots and reduces the service life and performance of the LED. Furthermore, the temperature difference between the metal layer and the heat-dissipation structure is also quite large, indicating that heat cannot be efficiently transferred to the heat-dissipation structure. On the contrary, through the heat distribution structure of this disclosure, due to the phase change and circulations of the working fluid in the heat distribution structure, spot heat source generated by the die can be distributed evenly, and thus efficiently transferred to the heat-dissipation structure.
In summary, the heat distribution structure of this disclosure and the heat distribution structure manufactured by the method for manufacturing a heat distribution structure of this disclosure have the ability of distributing heat evenly. The heat-dissipation module incorporating the heat distribution structure of this disclosure reduces heat resistance, eliminates hot spots and facilitates integration with the die manufacturing process, which are not only suitable for LEDs for increasing their performances, but for other spot heat sources, providing a better heat conductivity.
The above embodiments are only used to illustrate the principles of this disclosure, and they should not be construed as to limit this disclosure in any way. The above embodiments can be modified by those with ordinary skill in the art without departing from the scope of this disclosure as defined in the following appended claims.

Claims

What is claimed is:

1. A heat distribution structure comprising:

a first cap formed with a first groove and a second cap formed with a second groove, and a plurality of microstructures formed at bottoms of the first groove and the second groove;

a support body formed with a plurality of through holes interposed between the first cap and the second cap, wherein the first groove and the second groove face the support body, such that a cavity is formed by the first cap, the support body and the second cap; and

a working fluid accommodated in the cavity that flows within the cavity via the microstructures and the through holes.

2. The heat distribution structure of claim 1, wherein a plurality of microstructures are further formed on a sidewall of the first groove, a sidewall of the sealed groove, or the sidewalls of the first groove and the second groove.

3. The heat distribution structure of claim 1, wherein the cavity is in a vacuum state.

4. The heat distribution structure of claim 1, wherein the first and the second caps are made of silicon material.

5. The heat distribution structure of claim 1, wherein the support body is made of glass.

6. The heat distribution structure of claim 1, wherein the working fluid is water.

7. The heat distribution structure of claim 1, wherein the microstructures of the first groove and the second groove are protrusions.

8. The heat distribution structure of claim 1, wherein the first cap, the second cap and the support body are formed into an integrated structure by a high-temperature and high-pressure anodizing process.

9. A method for manufacturing a heat distribution structure, comprising the steps of:

(1) forming a plurality of microstructures at bottoms of a first groove of a first cap and a second groove of a second cap, forming a guiding hole on the first cap or the second cap, and forming a plurality of through holes in a support body;

(2) interposing the support body between the first cap and the second cap in a manner of the first groove and the second groove facing the support body, such that a cavity is formed between the first cap, the support body and the second cap; and

(3) introducing a working fluid into the cavity via the guiding hole, and then sealing the guiding hole, such that the working fluid flows within the cavity via the microstructures and the through holes.

10. The method for manufacturing a heat distribution structure of claim 9, wherein step (1) further comprises forming a plurality of microstructures in a sidewall of the first groove, a sidewall of the second groove, or the sidewalls of the first groove and the second groove.

11. The method for manufacturing a heat distribution structure of claim 9, wherein the forming of the microstructures at the bottoms of the first groove and the second groove is performed by etching.

12. The method for manufacturing a heat distribution structure of claim 9, wherein the forming of the through holes in the support body is performed by laser.

13. The method for manufacturing a heat distribution structure of claim 9, wherein the (2) further comprises combining the first cap and the second cap with the support body interposed therebetween under high temperature and high pressure.

14. The method for manufacturing a heat distribution structure of claim 9, wherein, before the sealing of the guiding hole in step (3), step (3) further comprises making the cavity in a vacuum state.

15. The method for manufacturing a heat distribution structure of claim 9, wherein the first cap and the second cap are made of silicon material by a lithography process.

16. A heat-dissipation module for dissipating heat generated by a die, the heat-dissipation module comprising:

a heat-dissipation structure;

a thermal interface material applied onto the heat-dissipation structure;

a heat distribution structure provided on the heat-dissipation structure with the thermal interface material interposed therebetween, and an insulating layer provided on a surface of the heat distribution structure away from the thermal interface material, wherein the heat distribution structure comprises:

a working fluid accommodated in the cavity that flows within the cavity via the microstructures and the through holes;

a metal layer formed on the insulating layer of the heat distribution structure; and

the die provided on the metal layer.

17. The heat-dissipation module of claim 16, wherein the die is a light emitting diode die.

18. The heat-dissipation module of claim 16, wherein the insulating layer is a silicon dioxide layer.